1. Field of the Invention
The present invention relates to a recording apparatus for an optical recording medium, and more particularly to a recording apparatus for an optical recording medium in which pre-pits that carry recording position information are formed in advance.
2. Description of the Related Art
At present, an optical recording medium having a recording capacity of several gigabytes is in practical use or under development such as a DVD-R (Digital Versatile Disc-Recordable) or a rewritable DVD-RW (DVD-Re-recordable). The remarkable improvement of the performance of the mass storage digital optical recording medium and the reproducing apparatus has made it possible to record a vast amount of data with a high quality.
On an optical disc as described above, there are formed a groove track constituting a recording track for information data and a land track constituting a guide track for guiding a light beam such as a laser beam constituting a reproduction beam or recording beam on the groove track. On the land track there are formed land pre-pits (hereinafter, simply referred to as pre-pits) corresponding to pre-information (pre-recording information). The pre-pits are formed prior to shipping of the optical disc and carry pre-information used by the recording/reproduction apparatus during recording/reproduction i.e. address and synchronization information for recognizing position on the groove track.
Furthermore, the groove track is wobbled with a frequency corresponding to the disc rotational speed. The wobbled groove track is formed prior to shipping of the optical disc in the same way as the pre-pits.
When information data is recorded on the optical disc, rotational control of the optical disc with a predetermined speed of rotation is effected by the information recording apparatus extracting the wobbling frequency of the groove track. Also, the information recording apparatus acquires the address information etc. indicating position on the optical disc where the recording information data is to be recorded, by acquiring beforehand pre-information by detecting the pre-pits. The information data is recorded on the corresponding recording position using the address information.
When recording the information data, recording of the information data is effected by forming information pits corresponding to the information data on the groove track by directing a light beam on to it such that the center of the light beam coincides with the center of the groove track. Part of the light beam is concurrently directed on the land track so that pre-information is acquired by detecting the pre-information from the pre-pits using for example a push-pull method, using the reflected light of the part of the light beam that is directed on the land track; a recording clock signal synchronized with the pre-pits is also acquired. Also, the information data to be recorded on the optical disc is divided into respective sync frames (hereinafter, simply referred to as frames) constituting pre-information units. The sync frames usually include synchronization information for achieving synchronization of each of the sync frames with the head position of the frames.
During the recording operation, mark portions and space portions are formed in accordance with a recording pulse signal. More specifically, a space portion corresponds to a binary xe2x80x9c0xe2x80x9d. A mark portion corresponds to a binary xe2x80x9c1xe2x80x9d which is formed with high output power laser beam. As described above, recording of information data is performed in this way by obtaining a recording clock synchronized with the pre-pits during recording. However, the quality of the pre-pit signal obtained from the mark portions is lower than that of the signal obtained from the space portions, due to changes in the amount of light of the recording pulse signal and changes in the coefficient of reflection produced by the pits. Consequently, only the pre-pit information of the space portions is extracted and utilized using gate circuitry or the like. However, as shown in FIG. 1, when a pre-pit pulse is extracted matching the space portions of the recording pulse signal, in some cases only a pre-pit pulse (PA) of incomplete shape is obtained. If a recording clock generated using such a pulse (PA) is employed, loss of synchronization or synchronization errors is produced, causing faults or a decrease in accuracy during recording and reproduction.
The present invention was made to overcome the above-described problems described above, and it is an object of the present invention to provide an optical recording media recording apparatus of high performance wherein recording of information data can be achieved without misalignment of the recording position.
To achieve the object, according to one aspect of the present invention, there is provided a recording apparatus for optical recording media in which pre-pits which carry recording position information are formed in advance and a data signal is recorded in accordance with the recording position information, which comprises a gate signal generating section for generating a gate signal in accordance with the data signal; a pre-pit signal generating section for generating a pre-pit signal from a signal read from the optical recording medium; a gate circuit for generating a pre-pit pulse train by allowing the pre-pit signal to pass therethrough in response to the gate signal; a pulse extractor for extracting pulses of predetermined waveform from the pre-pit pulse train; and a synchronization signal generating section for generating a recording synchronization signal based on the pulses of predetermined waveform.